Conventionally, as this type of walking assisting device, there is known a device including a load transfer portion and a leg link connected to the load transfer portion, wherein at least a part of the user's weight is supported by the leg link via the load transfer portion to reduce load on a user's leg so as to assist the user in walking (for example, refer to Japanese Patent Laid-Open No. 2003-220102). In this structure, the load transfer portion includes a waist support belt attached around a user's waist with a pair of left and right leg links connected to each other via first joints corresponding to human hip joints on both sides of the waist support belt in the lateral direction. The leg links are each formed of a freely bending and stretching link having a second joint corresponding to a human knee joint midway in the vertical direction. In addition, the leg link is connected to foot attachment portion which is attached to a user's foot at the lower end of the leg link via a third joint. Moreover, a driving source coaxial with the second joint is mounted on each leg link so as to generate weight relief assist force for supporting a part of the user's weight by means of a rotational drive of the second joint caused by the driving source.
Each leg link is generally formed in a length tailored to the length of a user's leg so that the leg link is stretched when the user is standing upright. This, however, causes a need to manufacture a dedicated device for an individual, which leads to an increase in cost. Therefore, it is desired that the leg links are each formed in such a length that the leg link is bent with the second joint projecting forward or backward of a reference line even if the user is standing upright, where the reference line is defined as a line connecting the forward/backward swing fulcrum of the leg link in the first joint to the third joint. According thereto, the height of the load transfer portion can be automatically adjusted in accordance with the user by controlling the driving source. Therefore, this eliminates the need for manufacturing a dedicated device for an individual, thereby achieving a versatile walking assisting device and lowering costs.
If the leg link is bent when the user is standing upright, however, the walking assisting device will have the following defects. Specifically, when the user is standing upright, the reference line is substantially vertical. Therefore, if the second joint projects forward of the reference line, the weight of the leg link including the driving source coaxial with the second joint generates a swing moment in a forward tilting direction around the third joint in the leg link, thereby applying a forward push force to the load transfer portion. Furthermore, if the second joint projects backward of the reference line, it generates a swing moment in a backward tilting direction around the third joint in the leg link, thereby applying a backward push force to the load transfer portion.